Process for generating sodium monoxide



Patented Aug. 3, 1954 UNITED STATES ATENT OFFICE PROCESS FOR GENERATING soDIUM MoNoxmE Application March 29, 1950, Serial No. 152,623

Claims. 1

This invention is a new and useful process for generating sodium monoxide and, inter alia, for generating sodium peroxide from the sodium monoxide so formed.

The invention will be fully understood from the following description read in conjunction with the drawing, which is a diagrammatic showing of apparatus in which the invention may be carried into elfect.

We have found that sodium reacts rapidly with sodium peroxide to form sodium monoxide at approximately 250 C. and above. In the iirst stage of our invention we maintain a mass of sodium peroxide in the state of continuous movement and/or agitation, and at a temperature above the melting point of sodium but below the said temperature at which sodium reacts rapidly with sodium peroxide. We preferably maintain a temperature in the said mass between 130 and 200 C. The mass of sodium peroxide is maintained in an atmosphere substantially free from oxygen and inert with respect to sodium peroxide and/or sodium. To this mass while so maintained in an inert atmosphere, we add sodium to the extent only of a minor part by weight of the sodium peroxide, and normally to the extent only of from l-10% by weight of the said peroxide. The amount of the sodium added is preferably from 3-8% by weight of the sodium peroxide. At this temperature and under these conditions the sodium does not react With peroxide or otherwise, but disseminatesV itself uniformly through the finely divided sodium peroxide, superfieially wetting the individual particles of peroxide. The sodium peroxide preferably is below 20 mesh.

In the next step of our process, the sodium peroxide carrying the said sodium, uniformly disseminated throughout, is elevated to a temperature at which reaction takes place between the said sodium and the said sodium peroxide, resulting in the formation of sodium monoxide. This reaction takes place at practical rates at 260 C. and at higher temperatures is almost instantaneous. While the reaction takes place almost instantly at higher temperatures, it is still preferable to exclude the presence of any oxidizing gas at this point, and we therefore preferably maintain the reactants at this stage in an atmosphere substantially free from oxygen and inert with respect to these materials.

These two steps are preferably carried out continuously by the continuous or intermittent addition of sodium and sodium peroxide to a mass of sodium peroxide in a condition of motion or agitation and by the continuous abstraction, from said mass, of sodium peroxide wetted with sodium, which is continuously introduced into a second mass of sodium peroxide and sodium undergoing reaction to sodium monoxide and held at a temperature at which the sodium and sodium peroxide react to form sodium monoxide.

While the two steps hereinbefore described may be used to produce sodium monoxide as the end product, they are preferably used as steps inthe manufacture of sodium peroxide, and for this purpose a part of the sodium monoxide formed in the second stage is continuously abstracted and preferably added continuously to a third maintained mass of sodium peroxide coated with sodium monoxide, which sodium monoxide is undergoing oxidation to the peroxide. For this purpose the third mass is maintained at a temperature between 250 and 490 C. and preferably from S50-425 C., and at this temperature is continuously contacted with a dry oxygen-containing gas, which may be either dry air or air which has been enriched in oxygen or relatively pure oxygen. The pressure of the atmosphere in contact with this mass is preferably slightly above atmospheric, although higher pressures may be employed and will in fact accelerate the oxidation reaction.

We prefer a cyclic process of oxidation in which sodium peroxide is continuously abstracted from the said third mass and in part returned with intermediate cooling to the said rst mass. The product of the process is of commercial quality running over 96% NazOz.

Referring to the drawing l designates a reactor of the rotary kiln type. The reactor is provided with circular rims 2 and 3 carried by anged wheels, such as 4 yand. 5. Some of the wheels are driven by suitable means (not shown) to impart a gradual turning movement to the reactor. Provision (not shown) is also made for heating the reactor to keep it at the desired operating temperature of from 400 to 430 C. Material may be introduced into the reactor from pipe l controlled by valve l discharging into worm conveyor 8 consisting of worm 9 driven by any suitable means diagrammatically indicated by ii and housed in pipe l2 which extends into the interior of the reactor. Pipe l2 is in turn surrounded by pipe I3. Pipes I2 and I3 collectively form an annular duct extending into the interior of the reactor connected to pipe I4 controlled by valve i5. The space between the exterior of pipe I3, which is stationary, and end I6 of reactor l, which is rotatable, is sealed by 3 stuffing box i?. At the other end 28 of the reactor, worm conveyor I9 extends to a point within the reactor. This consists of a worm 23 driven by any suitable means diagrammatically indicated by 2i housed in pipe 22 which extends to a point within the reactor and terminates in trough 23. Pipe 221s surrounded by pipe 2li. Pipes 22 and 2d collectively form an annular space extending into the interior of the reactor communicating with pipe 25 controlled by valve 25. rihe conveyor i8 discharges into pipe El. End 2Q of reactor i carries lifts 29 so that when the reactor is being rotated, solid material in the reactor will be lifted and discharged into the open top of trough 23, and can' thereby. be l removed from the reactor by operating the worin conveyor iii. Pipe 2l discharges into vibrating screens 3l. Of these the topmost screen 32 is of about 2) mesh and the material retained on this screen is diverted through pipe 33 to grinder diagrammaticaliy indicated by 34. Material passing through screen 32 is discharged onto screen 35, which is of about 40 mesh, and the material retained on screen 35, which will be approximatelyZO-i mesh, is discharged through chute 3% into tank El. Material passing through screen 35 which will be nner than 40 mesh is caught in pan ii and discharged thence through chute ft2 into pipe 53. Thev grinder 3s is operated to yield a product which will pass iii mesh,

and the combined products from grinder 3s and pan 4i are picked up and transported by enclosed conveyor 411, which may ce ci the socalled Redler type. Provision is made for cooling material transported by this conveyor, diagrammatically indicated by pipe i5 controlled by valve fit discharging through shower head fil, by which coolant may be distributed over the outer surface ofthe conveyor housing. The ccnveyor dei discharges into mixer 5i. of tank 52 'carrying mixer bar 53 driven by any suitable means diagrammatically indicated by t and provided with cover 55. The contents of the mixer may be held at any desired temperature by indirect heat exchange with liquid 'i circulating in jacket 5E. .Sodium may be introduced to mixer 5i, either continuously or intermittently, from tank 5i through pipe 53 controlled by valve 59. Any excess of material in mixer 5! yover that necessary to maintain the level indicated by line Si Will overiow through side outlet 52 and chute 83 into mixer'sl. This consists of tank 65 carrying mixer bar Q5 driven by any suitable means diagrammatically indicated by S. 3 and the contents of the tank may be held at any desired tempera-ture by indirect heat exchange with a liquid circulating in jacket ils. Material supplied to mixer @d over that necessary to maintain the level indicated by line 'li will overiiow through side outlet 'i2 into pipe 6. An inert gas, such as nitrogen, may be introduced through pipe 'i3 controlled by valve i4 to maintain an inert atmosphere in mixers 5l and Se passing thence counter-current to incoming material in conveyor ifi and discharging from the system through pipe '55 controlled oy valve it. Material may be introduced to mixer 5i through pipe 'Vi Acontrolled by valve Tt.

In starting the process nitrogen is fedthrough pipe 'I3 and exhausted through pipe iii until an inert atmosphere is present in mixers 5l and et, and in the'horizontal portion of conveyorrill. Dry air is fed into reactor l through pipe 25 until all moist air is displaced through pipe i4. n

This consists The tank is provided with cover i (lil 4 Then sodium peroxide is fed into reactor 5| until the level reaches 62, whereupon the peroxide overflows until the level reaches line 'H in reactor Gli and then the level builds up in reactor i to one-third to one-half of the depth of the reactor. The feeding of sodium peroxide is discontinued when 5l, 64 and l have reached normal levels indicated above. During this period the temperature in mixer 5i is brought vto 13D-225 C., preferably 13D-200 C., by circulationl of a suitable hot liquid in jacket 56; the temperature in mixer 64 is brought to at least 260 C., preferably between 260 and 400 C., by circulation of a suitable liquid in jacket 69; the

Vtemperature in' reactor l is brought to 250-490 C., preferably 40G-430 C., by indirect oil or gas iiring. rlhe auxiliary equipment including conveyor I9, screen 3|, grinder 34, conveyor 43, and coolingV system lil, are then started up and normal rates of flow established in the system.

Then sodium is fed continuously or intermittently through pipe k"i8 to the extent of 1-10%, preferably 3-8%, of the-feed of sodium peroxide into reactor 5i from conveyorlll. By operation of the mixer bar 53 the sodium -is thoroughly incorporated with the sodium peroxide at a temperature between '130 and 225 C., preferablyl between 13C-200 C. At this temperature the' sodium and sodium peroxide dol not react and the sodium Wets the particles of sodium peroxide superiicially, disseminating itself uniformly throughout the/mass.' As sodium peroxide'and sodium continue to be fed `into mixer 5i, theY excess overovvs through pipe 63 into reactor'- li, in which it is kept in a state of continuous agitation by mixer bar Se Vat a temperature above 260 C., preferably between 26 and 400 C. This causes reaction to take' place between thesedium peroxide and the sodium' on the surface,

with the resultant formation of` a superficial' Asmore sodium peroxide wetted with sodium is fed into this reactor and Aeach particle is converted tov layer or coating of sodium monoxide.

monoxide to a depth approximately equivalent stoichiometrically to the'percent of sodium originally on the surface, the product overiiowsf through sidevoutlet 12 into pipe ii/and is'transported by worm conveyor S intol reactor l.V They heat of reaction in the conversion step is suf-- iicient to raise the temperature to SOO-450 C. This temperature rise is advantageoussince it reduces heat requirements necessary in the next succeeding oxidation stage.

The contents of reactor i are held at a temperature between 250 andfiil()o C., preferably between 400 and 430 C. Dry oxidizingfgas 'such as air, air enriched'withioxygen, or pureoxygen is introduced through pipe, the residue thereof passing out of the system through pipehi.' The amount of oxygen so introduced is slightly greater stoichiometrically than thesodiuin` mon-v oxide simultaneouslyintroduced, with Vthe result-f ing conversionv ofthe entire material to sodium- (above 95% The'retentionV time in reactor-1! is-comsi peroxide of commercial quality NazOz). paratively short,I one-half to one and one-half hours, depending onpercentage sodium addition;A since only the superficial layer of monoxideon' the surface must be oxidized.-

The product passes through screen'13iwherevv the oversize material is scalped off by screen -32i ground in grinders .and returned to mixer' 5| screen 35.

prefer to use 20 mesh screen for 32 and 40 mesh screen for 35 but other screen sizes may be chosen. The above conditions are maintained and the system operated continuously until it becomes necessary to shut down for maintenance,

The foregoing description is for purposes of illustration and not of limitation and it is therefore oui intention that the invention be limited only by the appended claims or their equivalent wherein we have endeavored to claim broadly all inherent novelty.

We claim:

1. In the process of generating particles of sodium peroxide by the successive formation of a superficial layer of sodium monoxide followed by the oxidation of such layer of sodium monoxide with oxygen to sodium peroxide, the steps of mixing sodium with a larger amount by weight of sodium peroxide at a temperature above the melting point of sodium and below the temperature of reaction between sodium and sodium peroxide in an atmosphere substantially free from oxygen and inert with respect to sodium and sodium peroxide, thereby forming a film of sodium upon the particles of sodium peroxide and thereafter, while maintaining thereon an atmosphere substantially free from oxygen and inert with respect to sodium and sodium peroxide, elevating said sodium peroxide carrying said supercial film of metallic sodium to a temperature at which reaction takes place between said sodium and said sodium peroxide, thereby forming a superficial layer of sodium monoxide upon said particles of sodium peroxide.

2. Process according to claim 1 in which the said sodium mixed with said sodium peroxide is from l-% by weight of said sodium peroxide.

3. In the process of generating particles of sodium peroxide by the successive formation of a superficial layer of sodium monoxide followed by the oxidation of such layer of sodium monoxide with oxygen to sodium peroxide, the steps of mixing sodium with a larger amount by weight of sodium peroxide at a temperature above the melting point of sodium and below 250 Cgin an atmosphere substantially free from oxygen and inert with respect to sodium and sodium peroxide, thereby forming a film of sodium upon the particles of sodium peroxide and thereafter, while maintaining thereon an atmosphere substantially free from oxygen and inert with respect to sodium and sodium peroxide, elevating said sodium peroxide carrying said superficial iilm of me-Y tallic sodium to a temperature above 260 C. at which reaction takes place between said sodium and said sodium peroxide, thereby forming a superficial layer of sodium monoxide upon said particles of sodium peroxide.

4. Process according to claim 3 in which the said sodium mixed with said sodium peroxide is from l-l0% by weight of said sodium peroxide.

5. The cyclic process of generating sodium peroxide which comprises mixing sodium with a larger amount by weight of sodium peroxide in a maintained mass at a temperature above the melting point oi sodium and below the temperature of reaction between sodium and sodium peroxide, in an atmosphere substantially free from oxygen and inert with respect to sodium and sodium peroxide, thereby forming a film of sodium upon the particles of sodium peroxide in said mass, abstracting from said mass particles of sodium peroxide carrying a superficial iilm of metallic sodium and, while maintaining thereon an atmosphere substantially free from oxygen and inert with respect to sodium and sodium peroxide, elevating said particles to a temperature at which reaction takes place between said sodium and said sodium peroxide, thereby forming a superficial layer of sodium monoxide upon said particles of sodium peroxide, and thereafter introducing said particles of sodium peroxide carrying such superficial lm of sodium monoxide into a maintained mass of such particles in a dry oxidizing atmosphere and at a temperature at whichsodium monoxide oxldizes to sodium peroxide, maintaining the particles so introduced in said mass until the supercial film of sodium monoxide thereon has become substantially cornpletely oxidized by such atmosphere to sodium peroxide, withdrawing particles of sodium peroxide from said last mentioned maintained mass, abstracting a part of the same and recirculating the remainder to the said i'lrst mentioned maintained mass.

6. Process according to claim 5 in which the particles of sodium peroxide withdrawn from said last mentioned maintained mass are screened, particles of a size retained on said screen are withdrawn and particles of a size passing through said screen are recirculated to said first mentioned maintained mass.

7. The cyclic process of generating sodium peroxide which comprises mixing sodium with a larger amount by weight of sodium peroxide in a maintained mass at a temperature above the melting point of sodium and below 250 C., in an atmosphere substantially free from oxygen and inert with respect to sodium and sodium peroxide, thereby forming a nlm of sodium upon the particles of sodium peroxide in said mass, abstracting from said mass particles of sodium peroxide carrying a superiicial film of metallic sodium and, while maintaining thereon an atmosphere substantially free from oxygen and inert with respect to sodium and sodium peroxide, elevating said particles to a temperature above 260 C. at which reaction takes place between said sodium and said sodium peroxide, thereby forming a superficial layer of sodium monoxide upon said particles of sodium peroxide and thereafter introducing said particles of sodium peroxide carrying such supercial film of sodium monoxide into a maintained mass of such particles in a dry oxidizing atmosphere and at a temperature at which sodium monoxide oxidizes to sodium peroxide, maintaining the particles so introduced in said mass until the superficial film of sodium monoxide thereon has become substantially completely oxidized by such atmosphere to sodium peroxide, withdrawing the particles of sodium peroxide from said last mentioned maintained mass, abstracting a part of the same and recirculating the remainder to the said first mentioned maintained mass.

8. Process according to claim '7 in which the particles or sodium peroxide withdrawn from said last mentioned maintained mass are screened, particles of a size retained on said screen are withdrawn and particles of a size passing through said screen are recirculated to said first mentioned maintained mass.

9. A method for producing a product consisting essentially of particles having a sodium peroxide core and a relatively thin adherent outer layer of sodium monoxide said method comprising forming a thin layer of elemental sodium upon iinely divided sodium peroxide particles undergoing agitation, the weight of said sodium layer on each peroxide particle not exceeding 5% of the Weightfof theindividual sodium peroxide particle treated, at 'aftempera'ture above the melt# ing point of sodiumand below thetemperature of reaction between sodium and sodium peroxide in an atmosphere substantially free from oxygen and inert with respect to the sodium and sodium peroxide components, heating the resulting mixture of individual sodium peroxide particles of sodium peroxide with adherent layers of sodium to a temperature at which a chemical reaction takes place between. the sodium and said sodium peroxide, thereby forming the'supercial adherent layer of sodium monoxide upon said Particles of sodium peroxide.

10. A method forproducing a product consisting essentially of particles having a sodium peroxide core and a relatively thin adherentouter layer of sodium monoxide said method comprising forming a thin layer of elemental sodium upon nely divided sodium peroxide particles undergoing agitation., the weight of said sodium layer on each peroxide particle not exceeding 5% of the weight of the individual sodium peroxide particle treated, at a temperature above the melting` pointof sodium and below the temperature of reaction between sodium and sodium peroxide in an atmosphere substantially free from oxygen and inert with respect to the sodium and sodium peroxide-components, heating the resulting mixture of individual sodium' peroxide particles of sodium peroxide with adherent layers of sodium to a temperature at which a chemical reaction takes place between the sodium and saidsodium peroxide, thereby forming the supercial adherent layer of sodiummonoxide upon said particles of sodium peroxide, and thereafter subjecting said particles of sodium. peroxide carrying such Vsupercial layer of sodium monoxide to an oxidizing atmosphere and at a temperature at which sodium monoxide oxidizes to sodium peroxide `to form thereby particles of sodium peroxide.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 828,759 Meister Aug. 14, 1906 1,685,520 Carveth Sept. 25, 1928 FOREIGN PATENTS Number Country Date 264,724 Great Britain Jan, 27, 1927 265,124 Great Britain Mar. 17, 1927 505,734 Great Britain May 16, 1939 549,299 Great Britain Nov. 16, 1942 

1. IN THE PROCESS OF GENERATING PARTICLES OF SODIUM PEROXIDE BY THE SUCCESSIVE FORMATION OF A SUPERFICIAL LAYER OF SODIUM MONOXIDE FOLLOWED BY THE OXIDATION OF SUCH LAYER OF SODIUM MONOXIDE WITH OXYGEN TO SODIUM PEROXIDE, THE STEPS OF MIXING SODIUM WITH A LARGE AMOUNT BY WEIGHT OF SODIUM PEROXIDE AT A TEMPERATURE ABOVE THE MELTING POINT OF SODIUM AND BELOW THE TEMPERATURE OF REACTION BETWEEN SODIUM AND SODIUM PER OXIDE IN AN ATMOSPHERE SUBSTANTIALLY FREE FROM OXYGEN AND INERT WITH RESPECT TO SODIUM AND SODIUM PEROXIDE, THEREBY FORMING A FILM OF SODIUM UPON THE PARTICLES OF SODIUM PEROXIDE AND THEREAFTER, WHILE MAINTAINING THEREON AN ATMOSPHERE SUBSTANTIALLY FREE FROM OXYGEN AND INERT WITH RESPECT TO SODIUM AND SODIUM PEROXIDE, ELEVATING SAID SODIUM PEROXIDE CARRYING SAID SUPERFICIAL FILM OF METALLIC SODIUM TO A TEMPERATURE AT WHICH REACTION TAKES PLACE BETWEEN SAID SODIUM AND SAID SODIUM PEROXIDE, THEREBY FORMING A SUPERFICIAL LAYER OF SODIUM MONOXIDE UPON SAID PARTICLES OF SODIUM PEROXIDE. 